JP2002246924A - Satellite broadcasting receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satellite broadcasting receiver in which spurious levels are decreased. SOLUTION: A low noise down converter (LNB) of a satellite broadcasting receiver is formed on a substrate 92 attached to a chassis 94. The substrate 92 is covered with a frame 100 for shielding the substrate 92. Walls 84, 86 are provided on an input side and an output side of a mixer IC 82, and a height H2 of a spacer is set lower than in the other parts. Thus, radio waves broadcast traveling through the space are interrupted, and also absorption efficiency of radio waves by radio waves absorber 96 becomes better and spurious level is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite broadcast receiving apparatus, and more particularly, to a satellite broadcast receiving apparatus provided with a low noise down converter (LNB) used for satellite broadcasting and satellite communication.

[0002]

2. Description of the Related Art Radio waves are received by an antenna for satellite broadcasting,
A coaxial cable is usually used to guide a signal to an indoor BS tuner. However, radio waves received by an antenna cannot be guided indoors directly by a coaxial cable.

In order to guide a radio wave of a satellite broadcast having a very high frequency, it is necessary to use a metal tube called a waveguide. When a waveguide is used, a large hole needs to be made in a wall to guide a signal from an antenna to an indoor satellite broadcast receiver, and the attenuation is large, which is not practical. Therefore, usually, using the LNB installed near the antenna,
The frequency of the received signal is reduced to a frequency that can be guided by a coaxial cable, and the signal is transmitted to an indoor satellite broadcast receiver. An indoor satellite broadcast receiver has a built-in scramble decoder, which cancels scramble and displays an image on a display.

[0004] With the mixture of analog broadcasting and digital broadcasting, a wideband LNB is required to receive both signals. When converting a signal received from a satellite into a band to be received on the ground, a local oscillation circuit is used. However, the band of the signal received from the satellite is wider than the output band of one local oscillation circuit. Therefore, reception is usually performed using two local oscillation circuits having different oscillation frequencies.

For example, band 1 of a signal received from a satellite
For 0.7 to 11.7 GHz, the first local oscillation circuit having an oscillation frequency of 9.75 GHz covers the output frequency of LNB of 950 to 1950 MHz. Also, for the band of received signals of 11.7 to 12.75 GHz, 1
A second local oscillation circuit having an oscillation frequency of 0.6 GHz is used to cover the LNB output frequency of 1100 to 2150 MHz.

As described above, when two local oscillators are operated at the same time, a strong spurious signal may be generated and a harmonic may appear in the reception band. In this case, a normal signal from a satellite cannot be transmitted to a satellite broadcast receiving device having a built-in scramble decoder, and an image on a television or the like may be disturbed.

Conventionally, in order to suppress the spurious signal, measures have been taken such as attaching a large number of radio wave absorbers to all places on the side surface such as a chassis for mounting the substrate and a frame for covering the substrate in order to shield the substrate. I was

A signal input from the satellite to the LNB via the input horn is a low noise amplifier (LNA).
Amplifier) and band pass filter (BPF: Band)
PassFilter). The LNB is provided with a local oscillator, and the output of the local oscillator and the output of the BPF are provided to the mixer.

FIG. 8 is a diagram for explaining the arrangement of mixer circuits in a conventional LNB. Referring to FIG. 8, a high-frequency signal received from a satellite via an LNA and a BPF is input from RF signal line 76 to mixer IC 82. On the other hand, the local signal generated by the local oscillator is input from the local signal line 78 to the mixer IC 82.
The signal obtained by mixing the two is output to a thin output wiring 80.
To the next-stage select circuit.

A matching pattern is provided at an input portion of the select circuit so that an RF signal is not output. The wiring board on which the mixer IC 82 is mounted is covered with a frame for shielding. The frame has walls 70, 7 to reduce the interaction with adjacent circuits.
2, 74 are provided.

FIG. 9 is a sectional view schematically showing a section taken along line BB of FIG. Referring to FIG.
The RF signal line 7 is provided on the surface of the substrate 92 attached to the
6 and the wiring pattern of the local signal line 78 are formed. A mixer IC 82 is connected between the RF signal line 76 and the local signal line 78. The substrate is covered with a frame 500 for shielding the mixer IC 82, and a radio wave absorber 506 is attached to a ceiling portion of a space formed by the substrate and the frame, that is, inside the frame 500.

FIG. 10 is a layout diagram showing a signal transmission path from the local oscillation circuit 120 to the mixer IC 82 in the conventional LNB.

Referring to FIG. 10, local oscillation circuit 120
Is formed by a dielectric resonator 122, a strip line 124, a local IC 126, and a capacitor 128. Stripline 120 and dielectric resonator 122
Resonates, a local oscillation frequency is generated. This signal is provided to mixer IC 82 by local signal line 78. In order to prevent interference with other circuit parts, walls 72, 140, 1
42, 144 and 146 are formed.

[0014]

In the LNB, 2
It is necessary to reduce the level of spurious signals generated when operating more than one type of local oscillator as much as possible, and to transmit a normal signal from a satellite to an indoor satellite broadcast receiver having a built-in scramble decoder without being disturbed. .

For this reason, as shown in FIG.
In B, the radio wave absorber 506 is attached to the inside of the frame 500. However, since the frequency of the radio wave absorbed by the thickness of the radio wave absorber changes, if the ceiling of the space between the substrate and the frame is too high, the effect of absorbing the radio wave may be reduced.

An object of the present invention is to provide a satellite broadcast receiving apparatus capable of reducing the level of a spurious signal and outputting a signal from a satellite without interference.

[0017]

According to the present invention, a satellite broadcast receiving apparatus is provided corresponding to a plurality of local oscillation circuits and a plurality of local oscillation circuits, respectively. , At least a first local oscillation circuit that is one of the local oscillation circuits and a first mixer circuit that is one of the corresponding plurality of mixer circuits. A substrate, a conductive chassis on which the substrate is mounted, a conductive frame that covers an opposite side of the substrate from the side in contact with the chassis, and an RF signal line provided on the substrate for inputting an RF signal to the first mixer circuit. And the RF signal line includes a first wiring portion, and a second wiring portion located between the first wiring portion and the mixer circuit, and the frame connects the first mixer circuit to the substrate. The first frame between A second frame portion sandwiching the second wiring portion between the first frame portion and the substrate, wherein a distance between the second frame portion and the substrate is smaller than a distance between the first frame portion and the substrate. .

Preferably, the satellite broadcast receiving apparatus further includes a local signal line provided on the substrate for inputting an output of the first local oscillation circuit to the first mixer circuit, wherein the local signal line is connected to a third signal line. The frame includes a wiring portion, a fourth wiring portion located between the third wiring portion and the mixer circuit, and the frame further includes a third frame portion sandwiching the fourth wiring portion between the wiring portion and the substrate. The distance between the third frame portion and the substrate is smaller than the distance between the first frame portion and the substrate.

More preferably, the frame further includes a fourth frame portion sandwiching the first wiring portion with the substrate, and a fifth frame portion sandwiching the third wiring portion with the substrate. , The distance between the first frame portion and the substrate is the fourth
Is smaller than the distance between the frame portion and the substrate and the distance between the fifth frame portion and the substrate.

More preferably, the frame includes a fourth frame portion interposing the first wiring portion between the substrate and the substrate, a fifth frame portion interposing the third wiring portion between the substrate and the third frame portion, Sixth and seventh frame portions respectively covering regions on both sides of the wiring portion on the substrate, wherein the distance between the sixth frame portion and the substrate and the distance between the seventh frame portion and the substrate are 5 is smaller than the distance between the frame portion and the substrate.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

FIG. 1 is a block diagram showing a configuration of an LNB which is a satellite broadcast receiving apparatus according to the present invention.

Referring to FIG. 1, satellite broadcast receiving apparatus 1 includes:
A power supply circuit 20, an input horn 2 for receiving a signal from a satellite, a low noise amplifier (LNA: Low Noise Amplifier) 4 for amplifying the output of the input horn 2, and a band-pass filter (LNA) connected to the output of the LNA 4 BPF: Band Pas
s Filter) 8, a local oscillation circuit 12 that outputs a predetermined first local oscillation frequency, and a mixer that mixes the output of the band-pass filter 8 and the output of the local oscillation circuit 12.
10 is included.

The satellite broadcast receiving apparatus 1 further includes an LNA 4
A local oscillation circuit 18 for outputting a second predetermined local oscillation frequency;
Mixer 16 for mixing the output of band-pass filter 14 and the output of local oscillation circuit 18, select circuit 22 for selecting one of the outputs of mixers 10 and 16, and select circuit 2
IF amplifier 24 that amplifies the output of the second
And an F plug connector 28 connected to the other end of the capacitor 26.

A power supply potential is supplied from a power supply circuit 20 to the LNA 4, the local oscillation circuits 12, 18 and the F plug connector 28.

FIG. 2 is a side view showing the structure of the LNB which is a satellite broadcast receiving apparatus according to the present invention.

Referring to FIG. 2, an input unit horn 52 is mounted on chassis 32, and a substrate 34 is mounted on the upper surface. A frame 42 is attached so as to cover the substrate 34. A substrate 36 is mounted on the lower surface. Substrate 36
Is mounted so as to cover the frame. An F-plug connector 54 for outputting a signal to an indoor satellite broadcast receiver is further attached to the chassis 32.

As described above, the board 34 and the board 36 are separated by the metal shield by the chassis 32, and each circuit on the board is covered and divided by the frame so that radio waves do not fly outside.

FIG. 3 is a diagram showing a circuit arrangement provided on the substrate 34. With reference to FIG.
A region LNA where A4 is arranged, a region BPF1 where the bandpass filter 8 is arranged, a region LO1 where the local oscillation circuit 12 is arranged, and a region MIX1 where the mixer 10 is arranged.
An area SELECT for arranging the select circuit 22 and an IF
Area IF-AMP in which amplifier 24 is arranged, and power supply circuit 2
And a region POWERSUPLY in which 0 is arranged.

In the region POWERSUPLY, connection pins 62 and 64 are provided. A connection pin 66 is provided in an area SELECT where the select circuit is provided. The connection pin 64 is a connection pin provided for an RF signal. The connection pin 62 is a connection pin provided for connecting a power supply line. The connection pin 66 is a connection pin provided for an IF signal.

FIG. 4 is a diagram showing a circuit arrangement of the substrate 36 on which the second local oscillation circuit is mounted.

Referring to FIG. 4, substrate 36 is provided with region BPF2 in which band-pass filter 14 is arranged, region LO2 in which local oscillation circuit 18 is arranged, and region MIX2 in which mixer 16 is arranged. A connection pin 62 for receiving power supply, a connection pin 64 for receiving an RF signal from the substrate 34 side, and a connection pin 66 for returning an IF signal to the substrate 34 are provided.

That is, the signal sent from the board 34 to the board 36 via the connection pin 64 is limited to only the band required by the band-pass filter 14 in the area BPF2, and the local oscillation circuit 18 in the area LO2 and the mixer 16 in the area MIX2. IF
The IF signal is input to the select circuit 22 on the substrate 34 via the connection pin 66.

A power supply for operating the local oscillation circuit 18 is supplied from the substrate 34 to the substrate 36 via connection pins 62.
Is supplied to

FIG. 5 is a diagram showing an arrangement of the mixer IC 82 corresponding to the mixers 10 and 16 in FIG.

Referring to FIG. 5, LNA, BPF from satellite
The high-frequency signal received via the RF signal line 76
Is input to the mixer IC 82. On the other hand, the local signal generated by the local oscillator is input from the local signal line 78 to the mixer IC 82. The signal obtained by mixing the two is supplied to the next-stage select circuit through a thin output wiring 80.

At the input of the select circuit, a matching pattern is provided so that no RF signal is output. The wiring board on which the mixer IC 82 is mounted is covered with a frame for shielding. The frame has walls 70, 7 to reduce the interaction with adjacent circuits.
2, 74 are provided.

In the present invention, in addition to the conventional arrangement shown in FIG. 8, a wall 84 is provided between the mixer IC 82 and the RF signal line 76 to which the BPF is connected. A local signal line 78 to which a local oscillator is connected and a mixer IC
A wall portion 86 is provided between the wall portion 86.

FIG. 6 is a sectional view schematically showing a section taken along line AA of FIG. Referring to FIG. 6, a wiring pattern of RF signal line 76 and local signal line 78 is formed on the surface of substrate 92 attached to chassis 94. A mixer IC 82 is connected between the RF signal line 76 and the local signal line 78. Mixer IC8
The substrate is covered with a frame 100 for shielding the substrate 2, and radio wave absorbers 96 and 98 are attached to a ceiling portion of a space formed by the substrate and the frame, that is, inside the frame 100.

Frame 1 for shielding substrate 92
In 00, walls 84 and 86 are newly formed inside the frame as compared with the conventional structure shown in FIG. Also, the height H2 of the space between the frame portion where the mixer IC 82 is installed and the frame is smaller than the height H1 of the other portions. In other words, the ceiling of the frame 100 above the mixer IC 82 is lower than other parts.

By newly providing the wall portions 84 and 86, it is possible to block signals that fly through the space from the RF signal line side and the local signal line side to the mixer circuit. Therefore, it is difficult for the local signal and the local harmonic signal to enter the mixer circuit, and the interference is weakened and the spurious signal level is reduced.

Further, by lowering the ceiling of the space where the mixer IC is disposed, it is possible to more easily absorb the radio waves in the space by a radio wave absorber or the like. Also, Mixer IC
By providing walls on the RF signal line 76 side and the local signal line 78 side of 82 to enclose the space where the mixer circuit is arranged, the size of the radio wave absorber attached to the ceiling can be reduced.

FIG. 7 shows the LN of the satellite broadcast receiving apparatus of the present invention.
4B is a layout diagram illustrating a signal transmission path from the local oscillation circuit 120 to the mixer IC 82 in FIG.

Referring to FIG. 7, local oscillation circuit 120 includes:
It is formed by a dielectric resonator 122, a strip line 124, a local IC 126, and a capacitor 128. When the strip line 120 and the dielectric resonator 122 resonate, a local oscillation frequency is generated. This signal is supplied to the mixer IC 8 by the local signal line 78.
2 given. In order to prevent interference with other circuit portions, the frame covering the substrate has walls 72, 140, 142,
144 and 146 are formed.

FIG. 7 is different from the conventional structure described with reference to FIG.
I make 12,114. By making the length of the local signal line 78 longer than before and attaching a radio wave absorber to the ceiling of the passage of this signal line, local oscillation and local harmonics entering the mixer circuit can be achieved. Waves can be sufficiently suppressed spatially.

Therefore, it is possible to reduce a spurious signal level caused by interference between two types of local frequencies and local harmonics.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0048]

The satellite broadcast receiving apparatus according to the present invention has a built-in indoor scramble decoder in which spurious signals coming around the mixer in the LNB are removed or reduced, and the signal from the satellite is converted by the mixer without being disturbed. A normal signal can be sent to the satellite broadcast receiver.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an LNB which is a satellite broadcast receiving device of the present invention.

FIG. 2 is a side view showing a structure of an LNB which is a satellite broadcast receiving device of the present invention.

FIG. 3 is a diagram showing a circuit arrangement provided on a substrate 34;

FIG. 4 is a diagram showing a circuit arrangement of a substrate on which a second local oscillation circuit is mounted.

5 is a mixer I corresponding to the mixers 10 and 16 of FIG.
It is a figure showing arrangement of C82.

FIG. 6 is a sectional view schematically showing a section taken along line AA of FIG. 5;

FIG. 7 is a layout diagram illustrating a signal transmission path from a local oscillation circuit to a mixer IC in an LNB of the satellite broadcast receiving apparatus according to the present invention.

FIG. 8 is a diagram for explaining the arrangement of mixer circuits in a conventional LNB.

FIG. 9 is a sectional view schematically showing a section taken along line BB of FIG. 8;

FIG. 10 shows a local oscillation circuit 12 in a conventional LNB.
FIG. 3 is a layout diagram illustrating a signal transmission path from 0 to a mixer IC 82.

[Explanation of symbols]

1 satellite broadcast receiving device, 2 input horn, 8,14
Bandpass filter, 20 power supply circuit, 22 select circuit, 24 IF amplifier, 26 capacitor, 10, 1
6 mixer, 28 F plug connector, 12, 18 local oscillation circuit, 32, 94 chassis, 34, 36, 92 board, 42, 46 frame, 52 input horn, 54
F plug connector, 62, 64, 66 connection pin, 76
RF signal line, 78 local signal line, 80 output wiring, 84, 86, 70, 72, 74, 112, 11
4,140,142,144,146 wall, 100
Frame, 120, 124 Stripline, 120
Local oscillation circuit, 122 dielectric resonator, 62, 64 connection pin, 128 capacitor, 96, 98 radio wave absorber, 126 local IC, 82 mixer IC.

Claims (4)

[Claims] 1. A plurality of local oscillation circuits, respectively provided corresponding to the plurality of local oscillation circuits,
A plurality of mixer circuits for mixing an output of each of the local oscillation circuits and an RF signal; and a first local oscillation circuit which is one of the plurality of local oscillation circuits and a corresponding one of the plurality of mixer circuits. A substrate on which at least one first mixer circuit is mounted; a conductive chassis for mounting the substrate; a conductive frame for covering the opposite side of the substrate from the side in contact with the chassis; and a conductive frame provided on the substrate. And an RF signal line for inputting the RF signal to the first mixer circuit, wherein the RF signal line is located between a first wiring portion and the first wiring portion and the mixer circuit. A second frame portion, the first frame portion sandwiching the first mixer circuit between the substrate, and a second frame portion sandwiching the second wiring portion between the substrate. Frame part 2 And a distance between the second frame portion and the substrate is smaller than a distance between the first frame portion and the substrate. 2. A local signal line provided on the substrate, for inputting an output of the first local oscillation circuit to the first mixer circuit, wherein the local signal line is connected to a third wiring portion. A fourth wiring portion located between a third wiring portion and the mixer circuit;
Wherein the frame further includes a third frame portion sandwiching the fourth wiring portion between the substrate and the substrate, wherein the distance between the third frame portion and the substrate is 2. The satellite broadcast receiving device according to claim 1, wherein the distance is smaller than a distance between one frame portion and the substrate. 3. The frame, a fourth frame portion sandwiching the first wiring portion between the substrate and a fifth frame portion sandwiching the third wiring portion between the substrate and the substrate. The distance between the first frame portion and the substrate is smaller than the distance between the fourth frame portion and the substrate and the distance between a fifth frame portion and the substrate. The satellite broadcast receiving device as described in the above. 4. The frame, a fourth frame portion sandwiching the first wiring portion between the substrate and a fifth frame portion sandwiching the third wiring portion between the substrate and the substrate. And further comprising sixth and seventh frame portions respectively covering regions on both sides of the third wiring portion on the substrate, the distance between the sixth frame portion and the substrate, and the seventh frame portion. 3. The satellite broadcast receiving device according to claim 2, wherein a distance between the substrate and the substrate is smaller than a distance between the fifth frame portion and the substrate. 4.